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The Discovery of Rhabdopleura (Pterobranchia) in the Jurassic of Poland

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The Discovery of Rhabdopleura (Pterobranchia) in the Jurassic of Poland A eTA PAL A EON T 0 LOG I CAP 0 LON ICA Vol. XIV 1969 No.4 CYPRIAN KULICKI THE DISCOVERY OF RHABDOPLEURA (PTEROBRANCHIA) IN THE JURASSIC OF POLAND Abstract. - Fragments of tubarium of Rhabdopleura kozlowskii n.sp., etched from calcareous concretions occurring in Callovian clays in Lapiguz clay pit in Luk6w are described. Comparisons with the species Rh. vistulae Kozlowski from Danian of Poland and the Recent Rh. normani Allman fmm Norway have shown that Rh. kozlowskii n. sp. more strongly resemb1es the Recent species. INTRODUCTION The genus Rhabdopleura Allman, 1869 is represented in Recent seas by the following three species: 1) Rh. normani Allman, 1869, occurring in the northern hemisphere from the Lofoten to the Azores and from the western coasts of Greenland to the Bay of Biscay, where it lives at a depth of 5-600 m, temperature of 5-12°C and salinity of 33-35%0 (Burdon Jones, 1954); 2) Rh. striata Schepotieff, 1909, found on coral reefs near Ceylon at a depth of 2-15 m (Schepotieff, 1909); 3) Rh. annulata Norman, 1912, living near Celebes, New Zealand, Tasmania and the coasts of South Australia, at a depth of 75-549 m (Johnston, 1937; Hyman, 1959). We cannot be sure, however, if the species Rh. annulata is not conspecific with Rh. normani. If such would be the case, the genus Rhabdopleura would be represented in the Recent fauna by two species only. In the fossil state, only two species, i.e. Rh. eocenica Thomas & Davis, 1949 from Eocene of England and Rh. vistulae Kozlowski, 1956 from Danian of Poland have been known so far. Rh. kozlowskii n.sp., described in the present paper, is the third and the oldest representative of this genus found in the fossil state. Its remains were separated by etching from a calcareous concretion, about 30 kg in general weight, found in black Callovian clays in a clay pit Lapiguz in Luk6w about 100 km south-east of Warsaw. 538 CYPRIAN KULICKI The Callovian clays outcropped in Luk6w make up an erratic mass of northern origin 1 sq km in area, in Quaternary formation. The clays themselves are almost completely devoid of fauna, but the concretions, occurring in them, contain a rich and well-preserved fauna (ammonites, pelecypods, gastropods, belemnites) and, sometimes, even debris of wood. The concretions are also met with which apparently are unfossiliferous but, after dissolving them in hydrochloric acid, many spicules of sponges may be found in the residue. The concretions have varying diameters, on the average of 30 em. ClaJte~mineralsand bituminous substances they contain give them a black or gray colouration. Views concerning the stratigraphic position, origin of concretions and concentration of organisms they contain were presented by Makow­ slu--(1952). Ammonites from concretions, Kosmoceras jason (Reinecke), K. spinosum (Sowerby) and Peltoceras athleta (Philips)' determine the age of the days as the Middle and the lowermost part of the Upper Callovian. The effect of waving (Makowski, 1952, p. IX) was probably one of the conditions of forming concretions which would be an evidence of a not very great depth of the basin. Debris of wood and spores of land plants indicate a small distance from the shore. Approximate conditions of life of Rh. kozlowskii n. sp. may be reproduced on the basis of these facts. The remains of Rhabdopleura occur both in the concretions containing shells' of. molluscs and' fragments of wood and in those lacking such remains. Fragments of periderm of hydroids, scolecodonts, organic linings of tests of forminifers and abundant plant remains such as wood, macro­ spores, dinoflagellates, hystricospheres, cuticles and many other unident­ ified remains were etched together with the remains of Rhabdopleura from these some concretions. The colonies of Rh. kozlowskii n. sp. probably settled on shells of molluscs, pieces of wood and sponges which were resting on the bottom of a not very deep sea. Rh. kozlowskii n. sp. is likely to have identical ecological requirements with those of the Recent Rh. normani. The specimens of Rh. kozlowskii n. sp., described in the present paper, are housed at the Palaeozoological Institute of the Polish Academy of Sciences in Warsaw for which the abbreviation Z. Pal. is used. I would like to express my heartfelt thanks to Prof. R. Kozlowski (Palaeozoological Institute, Polish Academy of Sciences, Warsaw) and Docent A. Urbanek (Palaeozoological Laboratory of the Warsaw Univer­ sity) for their valuable remarks and advice which were very helpful in my work. THE DISCOVERY OF RHABDOPLEURA 539 DESCRIPTION FamiJIy Rhabdopleuridae Harmer, 1905 Genus Rhabdopleura- Allman, 1869 Rhabdopleura kozlowskii n. sp. (Text-figs. 1-6) Cotypi: A stolon in Fig. 4A; a zooidal tube in Fig. IE; a· stolonal tupe in Fig. 3B; cysts of sterile buds in Fig. 5J. Collection numbers: Z. Pal. Pb. 1/38, 45, ?9, 24. Locus typicus: Lapiguz clay pit, Luk6w, Poland. Stratum typicum: Callovian, Kosmoceras jason, K. spinosum and PeLioceras athLeta zones. Derivatio nominis: Named in honour of Prof..Roman Kozlowski, an investigator of fossil hemichordates. Diagnosis. - Zooidal and stolonal tubes similar.in size to those in Rh. normani. Fuselli of stolonal tubes much more frequently arcuate than those in Rh. vistulae, Rh. eocenica and Rh. normani. In transverse section, stolons semicircular as in Rh. normani. Peduncular stolons short and provided with 1-3 diaphragms. Material. - Fragmentary zooidal tubes - 340 speGimens; cysts of ster­ ile buds - 180; stolonal tubes - 35; zooidal tubes with a creeping part­ 11; stolons - 20. Description. - Zooidal tubes (Fig. 1). Broken and rarely occurring in fragments longer than 0.5 mm, not flattened. In regard to the state of preservation, they resemble zooidal tubes of Recent specimens from which they differ, however, in a much stronger pigmentation of the walls. In more.-l;han 60 measurements, the diameter of these tubes, the width of fusellar collars not taken into account, varied within limits of 115 and 207 I-l (on the average, 155 I-l). Together with fusellar collars, these dimensions amounted to 139-241 I-l (on the average, 182 I-l). The differen­ ces between these vah,les give a certain notion of the width of fusellar collars. Their width varies within limits of 12 and 21 /.1, the most often met with being 15 I-l wide. There is a certain interdependence between the diameter of tubes and width of collars: tubes with a small diameter have somewhat narrower fusellar collars than those in tubes with large diameters. The width of fuselli of zooidal tubes also displays a consider­ able variability: between 18 and 62 I-l (averaging 37 I-l). On the other hand, no correlation is observed between the diameter of tubes and the width of fuselli. Although the largest mean width of fuselli is recorded in tubes with a large diameter, the tubes with small diameters frequently have wider fuselli than those in tubes with larger diameters (Table 1). The thickness of walls of zooidal tubes, measured in optical sections, fluctuated within limits Of 7 and 14 I-l (averaging 10 I-l). The thickness o B c G \.~~-"7---J ........ -......",,-_£ O.5mm Fig'. 1. - Rhabdopleura kozlowskii n.sp. A-C zooidal tubes with small diameters (Z. Pal. Pb. 1/45-47), D-K zooidal tUbes with most frequent diameters (Pb. V33, 44, 48-52, 102), E a ootype. THE DISCOVERY OF RHABDOPLEURA 541 No. of spec. 20 '10 diem. ~n "u. 120 140 160 180 200 220 Fig. 2. - Frequency distribution <;urve of zooidal tubes diameter, drawn on the basis 'of specimens etched from two ·concretio·ns. of a wall, measured on microtomic sections amounts to 0.5-1.00 1-1-. This difference probably results from a decrease in the volume of the substance of which tubes are formed as an effect of dehydration of specimens in alcohol and xylene. The walls of zooidal tubes in the proximal part are always thicker than in the distal part. Zooidal tubes with smallest diameters (115-122 1-1-) considerably differ in appearance from the remain­ ing ones, their fuselli (Fig. 1 A-C) being wide in proportion to the diameter. The observation may be also made that the curve is bimodal: one with a diameter of 118 1-1-, and the other with a diameter of 168 1-1­ (Fig. 2). Stolonal tubes (Fig. 3). The basal wall of stolonal tubes, which during the animal's life time directly adheres to the substratum, is as a rule destroyed so that most specimens examined are devoid of it. Some of a few specimens with the basal wall preserved have also stolons. The wall itself is considerably thinner than the wall with a zigzag suture. One of the specimens is preserved together with a fragment~ry cyst of a sterile bud and three with septa. Almost all stolonal tubes are bordered by a narrow Ifarginal membrane. The width of these tubes measured on ten specimens, without taking into account the marginal membrane, fluctuates within limits of 126 and 163 1-1- (on the average, 145 1-1-). A still clearer idea concerning the width of stolonal tubes is imparted by the width of cysts of sterile buds which were enclosed in stolonal tubes and strongly adhered to their walls. These measurements, o i:, 3 3 Fig. 3 THE DISCOVERY OF RHABDOPLEURA 543 taken on a considerable number of specimens, display a fluctuation within limits of 97 and 255 J..L (averaging 162 J..L). The width of fuselli of stolonal tubes also displays a considerable variability (22-58 J..L, averaging 42 J..L). No smaller variability is recorded in the tubes which belong to one and the same colony (bifurcated tubes) and in which fuselli 49, 51, 51J..L wide occur succeeding each other.
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